Unipolar transistor



Mai-EH 12, 1963 E. G. RoKA UNIPOLAR TRANSISTOR File Aug. 17, 1954 llll 0h United States Patent OM 3,081,421 UNIPOLAR TRANSISTOR Edward G. Roka, Kokomo, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of [Delaware 1 Filed Aug. 17, 1954, Ser. No. 450,427

Claims. (Cl. 317-234) A u o e l n This invention rel-a'tes to seml-cond'u'ctors or transistors and more pa'nticul'arly to the unipola'r or analogue type of transistor. o

Although the junction and point contact type of transistors lare those mostly commonly refenred to and used, there i-s a funther ty'pe known as the unipolar or ana'logue type which is proving very useful. This 'type i's referred to as the analogue type because its action is more nearly analogou's to that of a vacuurn tu'be. In unip'o'lar 'transistors a crystal formed of a ptype section and annatype section is nsed with a potential applied across 'the crystal to 'cau'se current flow therethrough. Th'i's flow through the crystal may be' controlled 'by applying a junction across or 'around the crystal 'termed a ga'te junction 'and su'pplying 'a 'control voltage 'to the junction. The simil'ari- `ty 'to v'acuurn 'tu'be operation is ev'ident.

However, 'd'ffi'cnl'ties have 'been encoun'tered in 'secming proper 'closed junction ring 'construction on the unipolar 'type which is necessary 'to 'a'void insta'bility 'and dni'ft of 'the transistor.

I't is thcrefore 'an object in making this inventon to provide va 'unipolar transistor of new design which is very stalble.

It is a further object in making this inventon to provide 'a un'ipolar transistor in wh-i'ch the junction rings 'are applied to flat side surfaces of the crystal.

It 'is `a 'funther object in making |this inventon 'to provide c'ircnl'ar 'junction rings 'applied to the sides of Ia crystal to control 'the fiow .through 'the same.

With these 'an-d 'other objects 'in view which will Ibecome 'apparent `as the 'specification proceeds, my inventon will 'be 'best undenstood 'by reference to 'the following specification 'and cla'ims 'and the illustrations 'in 'the accompanying drawing's, in which:

'FlIGURE '1 'is 'a perspecti've view of 'a un-ipola'r transistor of .the 'conventional type.

FIGURE 2 is 'a perspective view of 'a unipolar transistor ernbody'in'g 'my inventon.

FIGURE 3 is 'a 'sectional view taken on 'the line 6-3 of FIGURE 2; 'and FIGURE 4 i's a circuit ldiagram ill'ustrating the connection of 'the transistor into 'a circuit.

The `unipo'lar transistor as i'l'lustra'ted 'in FIGURE 1 consists of 'a 'crystal of 'semisconductive material, such for example 'as germanium, which has |one 'area or region having p-type characteristics, 'and another 'a'rea joined thereto having n-type characteristics. The application of voltage 'across 'the crystal canses 'a fiow of current there'throu-gh.

Ohmi'c 'contacts 4 'and 6, which m'ay 'be of zinc, 'anti- 'mony or others on ntype 'sil'icon or 'germ-anium, `are alloyed or otherwise suitably secured to the opposite ends of the crystal. Lead wires 8 and I10 may 'be 'attachedlto the contact's. A `junction Iband 12, which may 'for exampl'e 'be of alu'minum, is alloyed around the central por'tion of the crystal 2. This junction band per-forms 'the |f'unction of 'a grid in 'a 'v'acu'um tube by aifecting the 'fiow of current through the 'crystal 'dependen-t 'upon the potential on said ring. In 'order for 'the ring to function properly and the 'transistor 'to 'be 'stable in its operation, the sides of the ring alt 14 ha've to 'be 'alloyed to said 'crystal and the corners of 'suficicnt depth to form 'a continuous conductiye ring 'around the crystal and 'adhered properly 43,081,421 Patented Mar. 12, 19 63 ICC 2 thereto throughoot i'ts length. This has proven diflicult 'to 'a'ttain.

I have therefore devised a new form of unipolar transistor as shown in FIGURES 2 and 3. In this form the the Semi-conductive crystal 16 has allcyed to one face thereof three separated areas of conductive material. The inner area 18 is circular and concentrically surrounding this -are two radially spaced circular rings 20 and 22. The surrounding conductive areas may of course be of any other Shape as long as they enclose the inner areas. The central 'area =18 and the outermost ring 22 provide olnnic contact 'areas and may be formed of, for example, zinc cobalt or other similar material, and the intermediate one 20, the junction ring, may be formed of aluminnm. On the opposite face of the crystal 16 -and in 'alignment therewith is `a second alloyed junction ring 24 formed of the same material. It will be obvious that 'any current fiow through the crystal from ohmic contact area 18 to area '22 must fiow between rin'gs 20 and 24 'and therefore the potential on these rings will control such fiow.

The connections of circuits to said crystal are shown in FIGURE 4. Line 26 is commonly connected to junction rings 2.0 `and 24. Line 28 is directly connected to ohmic ring 22. The input circuit is connected across lines 26 and 28. The load circuit 30 and a source of power indicated `a's a battery 32 'are connected across ohmic contacts 18 and 22. In this design the areas 18, 20, 22 and 24 are all flat areas on a relatively large surface that alloy well and form a good bond with no sharp corner Sections. The flo'w of current lthrough -the crystal from 'area 18 to 'area 22 all flows 'between rings 20 and 24 and is controlled by the potential on said rings.

This construction may also =be used as a junction type transistor instead of a unipolar type by connecting the contacts dilferently. The intermediate contact on one 'side may 'be connected to act as .the emitter electrode and the similar contact on the reverse side as the collector electrode. Any other contact or -contacts may be used as the 'base contact's in a junction type operation.

I claim:

l. A unipolar transistor comprising a flat serni-co'nductor crystal, an area of conductive material 'alloyed to one flat surface to form an ohmic contact therewith, a first ring of conductive material `alloyed to said flat surface spaced from said first larea and surrounding the same forming a junction contact therewith, a second ring of conductive 'material alloyed to the surface forming an ohmic contact therewith and spaced from the first and concentric therewith and a ring of conductive material |alloyed to the opposite face of the crystal for'ming a junction contact and substantially in alignment with the first-named ring on the first-named face.

2. A unipolar transistor comprisng a crystal formed of semiconductor material having flat side surfaces, an area of cobalt alloyed to one face of the crystal, a ring of aluminum valloyed to the crystal surrounding the firstnamed area and 'spaced therefrom, -a second ring formed of cobalt alloyed to the surface spaced from and surrounding said first ring and |a ring formed of aluminum alloyed to the cpposite face substantially in alignment with 'the first ring, said 'aluminum rings forming the junc- 'tion contacts for control.

3. A unipolar transistor comprising a crystal formed of sem-conductor material having flat side surfaces, an 'area of 'ohmic contact placed on one 'face of the crystal, 'a junction ring placed on the crystal surrounding the firstnamed area and spaced therefrom, a second ring of ohmic contact placed on the surface lspaced from and surrounding said first ring and a junction ring placed on the opposite face substantially inalign'ment with the first ring,

1 3 said junction ring-s forrning the junction contacts for control.

4. A signal translating device comprising a body ofl posedjbetween'said zones, and an annular region' ofsaidj oppositeV conductivity type disposedonthe opposite face o1fjs aid1body in alignment withithe first' mentioned region.

51 A signal` translating device comprising a body of semi-conductor material, a central ohmic contact'l zone and an annular ohrnic contactl zone circumscribing said' central zone on one face of^ the body, said` contact zones being adapted for connection with -an external load circuit' whereby an internal load circuit is defined'between said contact zonesV through said' body, said body having a rectifying junction contact of annular configurationl disposedibetweentsaid contact zones on said one face, and za rectifying junction contact of annular configuration disposed" oppositely ofA the first mentioned' rectifying junction contact on the opposite face of said lbody, said junction contacts being adapted for connection with -an exiternal control circuit whereby anelectric field may be established transverselyoffthe internal load circuit for control ofcurrent flow therein.

References Cited in the file of this patent UNITED STATES' PATENTS 2,600,500' Haynesetal June 17, 1952 2 ,6,4.4,914 Kircher July 7,l 1953 2,666;8j1^4` Shockley Ian, 19, 1954 2,6'72,528' Shockley Mar. 1:6, 1954` 2,709,12 32 Thedieck May 24, 1955 2;'l'54',4-31 Johnson V July 10, 1956 2353,730 Pantchechnikoff' Sept. 20, 1960 2',999',195 Saby Sept. 5, 1961 

1. A UNIPOLAR TRANSISTOR COMPRISING A FLAT SEMI-CONDUCTOR CRYSTAL, AN AREA OF CONDUCTIVE MATERIAL ALLOYED TO ONE FLAT SURFACE TO FORM AN OHMIC CONTACT THEREWITH, A FIRST RING OF CONDUCTIVE MATERIAL ALLOYED TO SAID FLAT SURFACE SPACED FROM SAID FIRST AREA AND SURROUNDING THE SAME FORMING A JUNCTION CONTACT THEREWITH, A SECOND RING OF CONDUCTIVE MATERIAL ALLOYED TO THE SURFACE FORMING AN OHMIC CONTACT THEREWITH AND SPACED FROM THE FIRST AND CONCENTRIC THEREWITH AND A RING OF CONDUCTIVE MATERIAL ALLOYED TO THE OPPOSITE FACE OF THE CRYSTAL FORMING A JUNCTION CONTACT AND SUBSTANTIALLY IN ALIGNMENT WITH THE FIRST-NAMED RING ON THE FIRST-NAMED FACE. 